[en] The feasibility of identifying and assaying alpha emitting nuclides, which are members of radioactive series with delayed states in the time range 10 ns to 0.2 s, by statistical and correlation counting techniques, has been investigated. The theory and practice of assay of low activities of such alpha emitters by scintillation techniques including the time interval analysis procedure and the counts distribution analysis procedure are discussed and described. Results are presented which have been obtained using these techniques to assay low level ²²⁸Th and ²²⁶Ra sources. (U.K.)